Fluid jet pump



May 7, 1935. HQKRAFT 2,000,762

FLUID JET PUMP Filed 061;. 26, 1935 'IIIIIIVIII/IIIIIIIIIIIII/ I I .llnrrl Inventor Hans Kraft H is Attorne g- Patented May 7, 1935 UNITED STATES PATENT FLUID JET PUMP Hans Kraft, Schenectady, N. Y., assignor to Gen-1 Yor eralkElectric Company. a corporation of New Application October 26, 1933, Serial No. 695,299

4 Claims.

The present invention relates to fluid jet pumps or injectors for conveying or compressing a fiuidby means of a fast-moving stream or streams of the same-or another fluid and con verting the velocity energy of the mixture into pressure energy in a diffuser.

In pumps or injectors of this type, in which the jet or jets of fast-moving or impelling fluid is discharged'centrally in the direction of the axis of the diffuser, instabilities occur due to the formation of a boundary layer of slowly moving fluid in the diffuser.

One object of the present invention is to provide an improved construction for pumps of the type above referred to in which the boundary layer is readily removed.

For a consideration of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto in vconnection with the accompanying drawing. I

In the single figure of the drawing I have shown a sectional view of a jet pump embodying my invention. The pump comprises a casing defining a suction chamber I having a suction inlet II for receiving fluid to be conveyed and a diffuser or discharge conduit l2. A noz-- zle I3 fastened to the casing by means of bolts l4 opens into the chamber in the direction of the axis of the difiuser.

The arrangement just described is generally known. in the art. During operation a fluid under pressure, that is, impelling fluid, is discharged through the openingor openings of the nozzle l3 into .the suction chamber H! where the jet or jets ejected from the nozzle l3 entrains and increase the velocity of the fluid entering the inlet II. The resulting mixture is forced into the diffuserin which it sufiers a reduction in velocity and an increase in pressure. A typical application of pumps of this kind is their use for conveying feed Water toa boiler-by means of elastic fluid received from the boiler and discharged through thenozzle l3 into the suction chamber. As pointed out above, the mixture of impelling fluid and fluid to be conveyed or compressed forms a boundary layer of fluid within the diffuser, which layer moves slowly or not at all. This formation of slowly moving fluid renders the pump unstable and reduces its efliciency.

In accordance with my invention the boundary layer is effectively removed or accelerated or impelled by the provision of an auxiliary nozzle, or nozzles for discharging impelling fluid in tangential direction along the wall of the difluser. The efiect of removing the fluid is improved by shaping the wall hyperboloidally and discharging the auxiliary jets of impelling fluid along the straight line element (generatrix) of the hyperboloidally shaped difiuser w'all.

Referring now to the arrangement in the drawing, the diffuser or discharge conduit has a' flanged portion l5 fastened to a flanged portion N5 of the suction chamber by means of bolts ll. According to my invention the two'flange's have recesses l8 and I 9 respectively. The two recesses or grooves deflne an annular channel connected to a conduit 2| for receiving impell-. ing fluid. Thechannel 20 opens into the diffuser for discharging an annular jet of impelling fluid in tangential direction along the diffuser wall. The diffuser wall, 22 is hyperboloidally shaped and forms a throat 23 near the discharge opening of the channel 20. The discharge of. impelling fluid along straight line elements of the hyperboloidally shaped difiuser wall is improved by the provision of a plurality of blades 24 near'the discharge opening of the channel 20. These blades 24 may be integrally formed with either the suction chamber or the diffuser. v

In the present arrangement I have shown a second auxiliary. nozzle arrangement 25 for removing or accelerating 'the boundary layer of slowly moving fluid. The nozzle arrangement 25 is axially spaced apart from the nozzle arrangement above described and more particularly is located on the other side of the throat 23 of the difiuser. nozzle arrangement may be accomplished in a simple manner by making the difiuser in two. halves, one half having a flanged portion 26 and the other half a flanged portion 21, each portion being provided with recesses forming an annular channel 28 connected to a conduit 29 for receiving impelling fluid. The channel opens into the diffuser and is provided near its discharge opening with a plurality of blades 39 for directing a plurality of jets of i'mpellingfluidalong straight line elements of the hyperboloidoccurring during the operation of an ordinary jet pump. Once a boundary layer has spent its velocity energy by overcoming the wall -fr1ct1on,

The provision of the second The expanding area along the wall is filled with highly turbulent liquid which converts'the velocity energy into heat, thus making the diffusing process extremely inefficient. To prevent this, each auxiliary nozzle arrangement sup plies fresh energy into the low velocity zone. This renders the operation of the pump more efficient, particularly where impelling fluids of different pressures are available. Besides the eificiency of the diffusing part, the pump efficiency depends largely upon the difference in velocity between the fluid in the diffuser and the impelling fluid injected into the difiuser from the auxiliary nozzles. The smaller this difference, the greater an efiiciency can be expected. During operation the supply of impelling fluid through the auxiliary nozzlearrangement or arrangements minimizes to a considerable extent the undesirable effects of the boundary layer in that it accelerates the velocity of the fluid near the wall of the diffuser or discharge conduit. The fluid to be conveyed or compressed is mixed and. carried along between the annular jet or jets of impelling fluid discharged from the auxiliary nozzle arrangement or arrangements and the central, axially directed jet of impelling fluid discharged from the main nozzle l3.

With my invention I have accomplished an improved construction for fluid jet pumps or injectors which are rendered more stable than ordinary jet pumps by the effective speeding up or removal of the boundary layer fluid. These pumps operate with greater efficiency, particularly when several auxiliary nozzles are arranged along the axis of the diffuser and impelling fluids of different pressures are available.

Having described the method of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters-Patent of the United States is:

of the chamber,

. ing a jet of impelling fluid 1. In a jet pump, a casing defining a suction chamber having an inlet and a discharge conduit with a flaring portion, a nozzle projecting into the suction chamber for discharging an impelling fluid in axial direction of the discharge conduit, and means for impelling a boundary layer of slowly moving fluid in the flaring portion of the discharge conduit comprising a ring of auxiliary nozzles for discharging impelling fluid in tangential direction along the wall of the flaring portion of the discharge conduit.

2. In a jet pump, a casing defining a suction chamber with an inlet for fluid to be conveyed and a flaring discharge conduit having a hyperboloidally shaped wall surface fastened to the chamber, a nozzle fastened to the chamber for discharging an impelling fluid along the axis of the discharge conduit, and means for impelling a boundary layer of slowly moving fluid along the wall of the flaring discharge conduit comprising nozzle means for discharging impelling fluid in tangential direction along the hyperboloidally shaped wall surface of the flaring discharge conduit.

3. In a jet pump, a casing defining a suction chamber with an inlet for fluid to be conveyed and a discharge conduit having a recessed flange portion fastened to a recessed flanged portion the recessed flanged portions defining a ring of nozzles for discharging an impelling fluid into the conduit, the discharge conduit having an inner hyperboloidally shaped surface and the nozzles being arranged to discharge in tangential direction towards said surface to minimize the formation of a boundary layer.

4. In a jet pump, a casing defining a suction chamber with an inlet for fluid to be conveyed and a discharge conduit, a nozzle for discharginto the chamber in the direction of the axis of the conduit, and means for impelling a boundary layer of fluid in the conduit comprising a plurality of axially spaced apart auxiliary nozzles for discharging impelling fluid of varying initial pressure in tangential direction along the inner wall surface of the discharge conduit.

HANS KRAFT. 

